All-Time Bestselling Books and Authors

Example Questions that can be answered by this FAQ:

What are the bestselling books of all time?

One should bear in mind that this question is basically unanswerable. No one really knows which books have sold the most copies in history, because we simply don’t have records that cover all of history! As such, any answer that we find is essentially just a "best guess" that is based upon estimates made by historians and other experts.